Speedfit Underfloor Heating FAQ

John Guest Speedfit have produced a list of frequently asked questions for their Underfloor heating.

How long does Underfloor Heating take to warm up a room from cold?

In high mass systems such as some screed floors the system can take 2 – 3 hours to heat up from cold.

After an initial heat up advanced controls maintain the screed temperature and with a process known as set back, reduces the room temperature by approx 4?C during periods of low demand such as overnight, allowing for a quicker heat up time the following morning.

How much heat will my underfloor heating system provide?

Typically, a screeded floor will emit a maximum of 100w/sqm. Timber floor structure will emit a maximum of 70w/ sqm.

What floor area can a manifold heat?

Manifolds are available to cater from 4 to 12 zones. A 12 zone manifold, feeding 12 heating loops can serve between 120 and 150 sqm of floor area. For larger systems use more than one manifold.

How long do I leave my underfloor heating on for during the day?

UFH is at its most efficient if left on 24 hours a day using room thermostats to control the comfort levels in each space or zone. Timers and programmers allow the user to choose when the heating is on or off or when to tell the system to reduce average temperature overnight, for example, known as set back. This saves energy and gives a faster up time the following morning.

Can I join pipes in the floor?

Pipes should not be joined in the floor.

How much water will be in my system?

Speedfit manufacture a 15mm pipe for use with underfloor heating. Every 1m of pipe contains 0.1L of water.

How much pipe do I need?

In a typical installation, pipe is laid at 200mm centres. This equates to approx 5 metres per sqm

Loops should be no longer than 100m. Speedfit will calculate the pipe spacing and loop lengths for each room or zone to meet the heat requirements of the space.

What is edge insulation used for?

Edge insulation is very important and is primarily used on screed floor systems.

It creates an insulation barrier around the perimeter of a room to prevent lateral heat loss and provide an expansion gap for the solid floor as it heats up and cools down.

Speedfit Edge insulation can also be used as an expansion medium on areas of screed floor in excess of 40 sqm.

What type of screed should I use?

Most screeds are a traditional sand and cement mix of 65 – 75 mm in thickness. Additives and binding agents are also used for added strength and flexibility.
Thinner screeds of 40 – 50 mm often known as pumped or liquid screeds are available. These offer better response times for underfloor heating and quicker drying time.

Specific advice should be sought from the screed manufacturer who will specify the correct screed for your project. Speedfit can discuss the options with you.

Do I need to add inhibitors to the system?

Yes, Speedfit advise that inhibitors should be used in all central heating systems including underfloor systems. Fernox and Betz Dearborn manufacture suitable products.

Where should the manifold be positioned?

The underfloor heating manifold can be located anywhere. However, to reduce pipe runs and achieve a balanced system it is preferable to locate the manifold as near as possible to the centre of the building.

What floor coverings can be used with UFH?

Almost all floor coverings will work with underfloor heating including carpets, stone tiles, laminate and natural wood. This gives you a virtually unlimited choice.
All materials have a resistance to heat transfer and this can be expressed as a TOG value – the same as for a duvet.

BSEN1264 states that floor coverings should be no greater than 1.5 TOGs.

However, experience has shown that many carpet and underlay combinations with high resistance work well with underfloor heating.

Always ask the floor covering supplier if their products are suitable for use with underfloor heating.

How much Insulation do I need?

The amount of insulation within a building is very important for an underfloor heating. A layer of insulation should be placed immediately below the heating pipes to minimise the downward heat loss of the floor and maximise the heat emitted upwards.

The total amount of insulation required is calculated in 2 parts. Firstly, the architect will specify the type and depth of installation to comply with the Building Regulations.

Secondly, the UFH system designer should specify any additional insulation layer required for the UFH to counteract the effect of the resistance of the floor and floor coverings above the heating pipes.

What Guarantees do Speedfit give?

As a result of long term test programmes and rigorous quality standards, John Guest Speedfit Limited offer a 25 year guarantee against the defects in materials or manufacturing of “PEM” “PSE” and “SFM” Range Plumbing Fittings and Speedfit Barrier Pipe manufactured by John Guest.

John Guest Underfloor Heating Products, which should be installed and maintained in accordance with our recommendations, carry a 2 year guarantee against defects in materials and manufacture.

John Guest Plumbing and Heating Products are for use with normal UK domestic plumbing and heating systems and are supplied in accordance with our Conditions of Sales.

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